Cosmetic brushes, depending on their intended use, require different shapes and styles in order to provide optimum application of product. To obtain the desired shape, most brushes are assembled first, and then the bristles are shaped. The shaping of the bristles is accomplished by a number of methods.
One method of shaping a brush is an actual mechanical cutting of the edges of the bristles with a knife or clippers. Most brushes are shaped in this manner. For example, when the bristles of a blush brush are assembled into a handle, the edges of the bristles are then trimmed by clippers into the desired shape. This is a time consuming process because the blades of the clippers need to be kept constantly sharp to provide a "clean" cut. Each time the blade wears down, the shaping process must be stopped so that the blades can be changed. This constant changing of parts has a definite negative impact on the number of units that can be produced, the ongoing quality, accuracy, and repeatability of those units, and the overall cost.
U.S. Pat. No. 5,020,551 discloses a method of manufacturing a mascara brush wherein the edges of the bristles are shaped by grinding. There are numerous drawbacks with the use of this method of shaping the edges of the bristles. The major disadvantage to using this method is the lack of accuracy with which the bristles can be shaped. In order to effectively shape the bristles using this method, the bristles have to be a certain stiffness and structure, thus, the bristles used cannot be soft. Second, the bristle brush surface cannot be intricately cut along its length with a grinding wheel. The shaping of a brush using a grinding wheel limits the cutting to broad surface cuts, generally 3 to 4 turns of the wire core. Additionally, the use of a grinding wheel, if not controlled precisely, will cause a build up of excessive heat which will cause the bristles to melt or deform, thus making the brush useless. Also, using a grinding wheel to shape the brush will not ensure the same shape for each brush produced. As the grinding wheel wears down, each brush will vary slightly from the previous one, thereby making the last brush produced significantly different from the first brush produced from the same grinding wheel. Additionally, the process of grinding the bristles to form a particular brush shape is a slow process.
Another method of shaping the edges of a brush, as disclosed in U.S. Pat. No. 5,197,497 and U.S. Pat. No. 5,345,644, is via a radiant heat source. This method is mainly used with synthetic fibers, such as plastics. With this method, a heat source is provided which is directed at the edges of the bristles. When the bristles reach their melting point the ends begin to curl over. This causes the length of the bristle to shorten and also creates a burr at the tip of the bristle. This burr negatively affects application of the product because, while combing the lashes, the burr will pull at the lashes thereby making application uncomfortable to the consumer. Depending on the temperature and duration of the heat source in a particular location, different shapes can be obtained. This method of manufacture is not always desirable because it does not allow for a great degree of control over the length of the bristles. Slight imperfections in the bristles themselves will cause the bristles to deform and melt at different rates, thereby causing each bristle to be a different length. Also, when bristles are shaped in this manner they very often fuse together during the melting process.
In contrast to previous methods, the present invention provides a precise, accurate, reliable, and consistent method of manufacturing a brush.
The present invention also provides a method of manufacturing a brush which allows a greater degree of flexibility in the design chosen for the bristles.
Further, this invention provides a method of manufacturing a brush which can be adapted for use with any cosmetic brush.
Also, this invention provides a method of manufacturing a brush which is economically advantageous.